Last interglacial hydroclimatic changes in Southeast Africa and potential impact on early human migration
Final Report Abstract
Hydroclimate conditions in subtropical Southeast Africa are generally considered to be significantly affected by future global warming. However, the extent of these hydroclimatic changes is still difficult to assess because of ambiguous proxy records and climate simulations for past warm episodes. In this context, a thorough investigation of regional hydroclimate variability during the Penultimate Interglacial, the Eemian or Marine Isotope Stage (MIS) 5e, the most recent time interval with higher temperatures than today, might provide important information also about the response of the regional hydroclimate climate under future warming scenarios. To reconstruct past hydroclimatic changes in subtropical Southeast Africa for MIS5e, we analysed the stable hydrogen isotope composition (δD) of the long-chain n-alkanes n-C27, n-C29, n-C33 and n-C33 that are preserved in sediments recovered at IODP Site U1477, located ~85 km off the Zambezi River delta in the Mozambique Channel. Longchain n-alkanes are major components of the leaf waxes of higher terrestrial plants and transported from the continent to the ocean by the Zambezi River. The n-alkane δD primarily reflects amountcontrolled changes in the δD of regional precipitation at the time of plant growth and can therefore be used to reconstruct past hydroclimate variability in the Zambezi River catchment. In addition, the stable carbon isotope composition (δ13C) of the long-chain n-alkanes allows to track past vegetation changes, i.e., variations in the relative abundance of C3 (e.g., trees) and C4 plants (e.g., savanna grasses). Our results provide evidence for a considerable hydroclimate variability in Southeast Africa across the Penultimate Interglacial. The temporal correspondence of supposedly dry episodes in the region with wet intervals in Northeast Africa indicates that the northward migration of Congo Air Boundary associated with a similar shift of the Inner Tropical Convergence Zone was the major control for Southeast African rainfall changes, rather than last interglacial sea surface warming in the western Indian Ocean.
Publications
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Higher sea surface temperature in the Indian Ocean during the Last Interglacial weakened the South Asian monsoon. Proceedings of the National Academy of Sciences, 119(10).
Wang, Yiming V.; Larsen, Thomas; Lauterbach, Stefan; Andersen, Nils; Blanz, Thomas; Krebs-Kanzow, Uta; Gierz, Paul & Schneider, Ralph R.
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Hydroclimate and vegetation changes in SE Africa across the last interglacial period reconstructed from the sediment record of IODP Site U1477, Mozambique Channel. In: Schwab, M. J., Kallmeyer, J., Krastel, S., Bornemann, A. (Eds.) (2022): IODP/ICDP Kolloquium, Nov. 1-3, 2022, Potsdam, Abstract Volume, (Scientific Technical Report STR; 22/07), p. 45
Lauterbach, S.; Andersen, N.; Blanz, T.; Van der Lubbe, J. & Schneider, R.
